Process of purifying aluminous materials.



\ No Drawing.

eme itus PATENT onnrcn;

LEWIS E. SAUNDERS, 0F NIAGARA FALLS, NEW YORK, ASSIGNOR T0 NORTON COMPANY, OF WORCESTER, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

PROCESS OF PURIFYING ALUMINOUS MATERIALS.

T0 allwhom it may concern:

Be it known that I, LEWIS E. SAUNDERS,

a citizen of the United States, residing at Niagara Falls, in the county of Nia ara and State of New York, have invente certain new and useful Improvements in Processes of Purifying Aluminous Materials, of which the following is a specification.

In my prior United States Patent No.

960,712, patented June 7, 1910, I have de- I .wise reduced to carbid (or to equivalent reduction products including the hypothetical aluminum suboxid not as yet certainly identified) and it is believed that these reduction products of alumina are the edective reducing agents for the elimination of the last portions of the above mentioned non-aluminous oxids, and more particularly of the diflicultly reducible oxid of titanium. The non-aluminous reduced products segregate for the most part from the bath, which then consists of molten alumina and its reduction products, or of the latter alone in case a suficient proportion of carbon has been used. The aluminous bath is then subjected in a second operating stage to a treatment by oxidation whereby the reduction products of alumina are reconverted into alumina.

According to my prior patent, this oxida tion was preferably accomplished by means of a aseous oxidizing agent, as for example by b owing air through the molten bath in the furnace.

The present invention is a specific improvement upon the process of the abovementioned patent, the improvement consisting in the substitution for air or other gaseous oxidizing agent, of a solid oxygen-containing substance.

The oxidizing addition should be added in suficient proportion to edect the complete oxidation to alumina of the reductionprodnets of alumina remaining at the close of the first operating stage. As such oxidizing addition I may employ iron oxid, or any of Specification of Letters Patent. Patented June llll, llgllfi.

Application filed August 18, 1917. Serial No. 186,921. 7

the normal oxid-impurities of bauxite, these being thereby reduced to the corresponding metal or alloy, and for the greater part at least separating out beneath the purified bath. Or I may use oxygen-containing salts or compounds of metals which are volatile under the furnacing conditions, and which are therefore largely eliminated from the charge. Among such compounds I may inention sodium carbonate, zinc oxid and the ike.

Instead of using the oxids of iron, silicon or titanium in their naturally occurring forms, or mixtures thereof, I may employ these oxids in the mixture in which they exist in bauxite. In this case I incorporate with the highly reduced product of the first operating stage such a proportion of calcined bauxite that the non-aluminous oxids therein will at least suflice for the re oxidation of the aluminous reduction products. The mixture is then subjected to electric furnace fusion, yielding directly a commercially pure product containing not only the alumina of the first-stage charge, but also the alumina of the oxidizing addition. It is even desirable in some cases, as when a very tough and strong-grained product is desired, to use the bauxite in decided excess of the amount necessary to re-oxidize the reduction products of alumina. In case this is done the final fused product will of course carry a proportionate amount of the nonaluminous oxids of the bauxite addition.

Or as a further modification, the bauxite or other oxidizing additions may be used in excess in the second operating stage as above described, but in conjunction with such quantity of carbon as may be necessary to reduce the undesired excess of nonaluminous oxids. In this case the carbon should not be used in suficient proportion to reduce the whole of the excess of nonaluminous oxids in the bauxite, since under such conditions there would be a further formation of reduction products of alumina. These and other modifications of the process may be made without departing from the spirit of my invention. It is one of the operating advantages of this process that great latitude is afforded not merely in from highly impure raw materials, including' clays and sllicious bauxites, an aluminous abrasive containing upward of 97 per cent. of alumina.

I claim 1. The process of purifying aluminous materials, which consists in fusing the same in presence of a suflicient proportlon of carhon to effect a substantial reduction of the alumina, separating-the reduced impurities, and then re-oxidizing the reduction roducts of alumina by electric furnace usion with a solid oxidizing addition.

2. The. process of purifying aluminous materials, which consists in fusing the same in presence of a sufiicient proportion of carbon to efi'ect asubstantial reduction of the alumina, separating the reduced impurities, and then re-oxidizing the reduction products of alumina by electric furnace fusion with bauxite,

3. The process of purifying aluminous materials, which consists in fusing the same in presence of a suflicient proportionof carton to efiect a substantial reduction of the Laeaaae alumina, separating the reduced impurities, and then re-oxidizing the reduction products of alumina by electric furnace fusion with bauxite, the bauxite in such proportion that the non-aluminous oxids thereof are in excess of the quantity necessary for the reoxidation.

4. The process of purifying aluminous materials, which consists in fusing the same in presence of a sufiicient proportlon of carbon to efi'ect a substantial reduction of the alumina, separating the reduced impurities, and then re-oxidizin the reduction products of alumina by e ectric furnace fusion with bauxite admixed with carbon, the bauxite in such proportion that the nonaluminous oxids thereof are in excess of the quantity necessary for the re-oxidation, and the carbon in proportion to reduce a part only of the excess of-non-aluminous oxids in the bauxite.

In testimony whereof, I ture.

afix my signa- LEWIS n. expanses. 

